(CNN) -- The U.S. State Department issued a travel alert for Jamaica on Friday, citing unconfirmed reports of criminal gang members amassing in Kingston and the mobilization of Jamaican defense forces.

"If the situation ignites, there is a possibility of severe disruptions of movement within Kingston, including blocking of access roads to the Norman Manley International Airport," according to the alert.

"The possibility exists that unrest could spread beyond the general Kingston area," the alert said.

The U.S. Embassy in Kingston, Jamaica's capital, is taking extra security precautions, according to the alert, which expires June 21.

"American citizens should consider the risks associated with travel to and within the greater Kingston metropolitan area," the alert said. "U.S. citizens in Jamaica are advised to monitor local news reports and consider the level of security present when venturing outside their residence or hotel."

The United Kingdom on Thursday updated its travel advisory for British citizens in Jamaica.

The British Foreign Office urged UK citizens to take extra care when traveling away from their homes or hotels due to the "increased risk of civil disorder and street violence in Kingston" and potentially other urban areas.